The present invention relates generally to electric motors, and particularly to a stator assembly that facilitates motor construction.
Rotary electric motors are typically comprised of two primary components, a rotor and a stator. The stator is used to produce a rotating magnetic field. The rotating magnetic field induces a rotating force on the rotor that causes the rotor to rotate about an axis. The rotational motion of the rotor can be drivingly coupled to an external device, such as a pump.
The stator is typically constructed of conductors wound longitudinally around a core. These longitudinally wound conductors are spaced radially around the stator. The core typically is constructed from metallic laminations that have been stacked and pressed together. The laminations are manufactured with a pattern of openings so that when the laminations are stacked the individual openings form a pattern of continuous longitudinal openings extending through the lamination stack. Typically, the rotor is housed within a cavity formed by a center opening through the laminations. The conductors are wound through longitudinal conductor openings that are disposed around the central opening. The metallic laminations help to couple the magnetic field produced by the conductors to the rotor.
To operate the electric motor, the conductive wiring in the stator is coupled to an electrical power source. A magnetic field is produced from the electricity flowing through the conductive wiring. In an exemplary embodiment, the electrical power source provides three-phase alternating current. As the three phases of the alternating current cycle radially around the stator, the conductors produce a rotating magnetic field in the stator.
The required size of the stator and rotor depends on the amount of work needed from the motor. The strength of the motor is determined, primarily, from the strength of the magnetic field that can be produced by the stator. The strength of the magnetic field produced by the stator is, in turn, affected by the number of turns of the conductive wiring. All other factors being the same, the greater the number of turns the stronger the magnetic field produced.
A submersible electric motor for use in a submersible pumping system may be required to lift wellbore fluids from depths of several thousand feet. A conventional motor that could otherwise be used to provide the equivalent pumping power on the surface cannot be used in a wellbore, because the number of turns of conductive wiring needed to produce the required force would require a motor of such a large diameter that it would be too wide to fit into the wellbore. Therefore, instead of a relatively short, thick motor with a large number of turns, the stators of submersible electric motors are extremely elongated with a smaller number of turns. Elongating the stator allows the motor to produce the required force to drive a pump by developing the magnetic force over a much greater length.
Currently, electric motors, particularly elongate motors such as those used in submersible electrical pumping systems for pumping petroleum, are constructed with unitary stators. Depending on the horsepower required of the motor, electric submersible pumping system motors can utilize stator assemblies thirty feet long or more.
Traditionally, the stator assemblies have been constructed by stacking individual stator laminations together to form a stator of a desired length. The lamination stack is then inserted into the stator housing. The lamination stack is then compressed and maintained under compression within the stator housing. Maintaining the laminations under compression prevents the laminations from spinning freely inside the stator housing. However, constructing a stator in this manner can be problematic. The sheer size of the stator makes manipulating the stator components difficult. Furthermore, loading the stator laminations into the stator housing by hand is time consuming and difficult.
Therefore, it would be advantageous to have a method and system to facilitate assembly of the stator of an elongated, submersible electric motor of the type used with electric submersible pumping systems.
Certain aspects commensurate in scope with the originally claimed invention are set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of certain forms the invention might take and that these aspects are not intended to limit the scope of the invention. Indeed, the invention may encompass a variety of aspects that may not be set forth below.
According to one aspect of the present invention, a method is featured for manufacturing a stator for a submersible electric motor. The method includes placing stator laminations disposed over a mandrel into an automated stator press. The automated stator press has a hydraulic ram and an automatic control system. The method includes placing the stator laminations, while disposed over a mandrel, into a stator housing. The method also includes using the hydraulic ram to compress the stator laminations within the stator housing, and automatically controlling the compression of the stator laminations with the automatic control system. Further, a stop is placed into the stator housing to maintain the stator laminations in a state of compression after the force of the hydraulic ram is removed. The method also includes removing the force of the hydraulic ram and removing the mandrel from the stator housing.
According to another aspect of the invention, a method of manufacturing an electric motor is featured. The method includes placing stator laminations, disposed over a mandrel, into an automated stator press. The automated stator press has a hydraulic ram and an automatic control system to compress the stator laminations within a stator housing. The compression of the stator laminations is controlled with the automatic control system. The method further includes placing a stop into the stator housing to maintain the stator laminations in a state of compression after the force of the hydraulic ram is removed. Electrical conductors are routed through aligned openings in the plurality of laminations.
According to another aspect of the present invention, a system is featured for assembling stator laminations in a stator housing. The system includes an automated stator press to compress laminations in a stator housing. The stator press utilizes a mandrel upon which a plurality of stator laminations may be located. The system also includes a support frame to support the stator laminations when placed on the mandrel. A control system is designed to automatically operate a hydraulic ram positioned to compress the plurality of stator laminations to a desired length within the stator housing.